The present invention relates to valves and in particular to heart valve prostheses having a plurality of flexible leaflets.
Ever since 1950, when blood oxygenators made open heart surgery feasible, it has been possible to treat some forms of heart disease by replacing one of the patient""s heart valves with a prosthetic valve. Early heart valve prostheses included ball-and-cage valves and disc-and-cage valves in which a ball or a disc was housed in a cage. One side of the cage provided an orifice through which blood flowed either into or out of the heart, depending on the valve being replaced. When blood flowed in a forward direction, the energy of the blood flow forced the ball or disc to the back of the cage allowing blood to flow through the valve. When blood attempted to flow in a reverse direction, or regurgitate, the energy of the blood flow forced the ball or disc into the orifice in the valve and blocked the flow of blood.
A tri-leaflet valve includes an annular valve body in which three leaflets are mounted to a portion of the valve body, called a stent, located at the circumference of the annulus. The edge of each leaflet which is mounted to the valve body is called the attachment edge. Any edge of a leaflet which is not mounted to a valve body is called a xe2x80x9cfree margin.xe2x80x9d When blood flows in the forward direction, the energy of the blood flow deflects the three leaflets away from the center of the annulus and allows blood to flow therethrough. When blood flows in the reverse direction, the three leaflets engage each other in coaptive regions in which the free margins of the leaflets abut each other, occlude the valve body annulus and prevent the flow of blood. The valve leaflets are made from tissue, such as specially treated porcine or bovine pericardial tissue, or from man-made materials such as ceramic materials, elastomers or other biocompatible polymers.
One difficulty with valve prostheses is the amount of force required to open the leaflets to allow blood flow therethrough. Similarly, another issue is the amount of force required to close the leaflets. In conventional tri-leaflet valves, for example, the amount of force required to open the leaflets can be relatively high. This requirement is present in those valves made of polymeric material which include leaflets which present a convex or dome surface to the flow of blood in the forward direction when the leaflets are in a closed position. The amount of pressure needed to overcome the resistance to opening which is present due to the presentation of a dome to the blood flow is greater than other geometries. This excess pressure requirement can hinder the functioning of the valve and may prevent the valve from opening when necessary due to lack of sufficient force provided by the blood flow.
In addition, it is often important that the valve begin opening at a free margin of one or more of the leaflets. This enables blood flow to proceed as soon as a force of the blood flow acts on the leaflets because the free margins are open. If the initial blood flow acts on the lower portion of the leaflets and begins the opening sequence away from the free margin, then blood flow through the valve is delayed until the force finally displaces the free margins.
Therefore, there is a need to provide a heart valve prosthesis design to reduce the forward (systolic) pressure necessary to open the heart valve.
In general, in one aspect, the invention can include a heart valve comprising a valve body having a plurality of leaflets. The plurality of leaflets can be coupled to the valve body, and each of the plurality of leaflets is capable of having an open position and a closed position. One or more of the plurality of leaflets can have two or more features. The features can be formed as part of the leaflets.
In another aspect, the heart valve described above can have only two features.
In general, in one aspect, the invention can include a heart valve comprising a valve body having a plurality of leaflets. The plurality of leaflets can be coupled to the valve body, and each of the plurality of leaflets is capable of having an open position and a closed position. One or more of the plurality of leaflets can have two or more features, and the two or more features comprise one or more of the group consisting of planar regions, semicircular regions, folded regions, peaked regions, ridged regions, regions that are thicker than the rest of the leaflet, regions that are thinner than the rest of the leaflet and sine-wave shaped regions.
In general, in another aspect, the invention can include a heart valve comprising a valve body having a plurality of leaflets. The plurality of leaflets can be coupled to the valve body, and each of the plurality of leaflets is capable of having an open position and a closed position. One or more of the plurality of leaflets can have two or more features. Each of the plurality of the leaflets can have a line that extends from the bottom point of the leaflet to the center of the free margin. In one aspect, the two or more features are symmetrically disposed around this line of the one or more of the plurality of leaflets. In another aspect, the two or more features are asymmetrically disposed around this line of the one or more of the plurality of leaflets.
In general, in another aspect, the invention can include a heart valve comprising a valve body. A plurality of leaflets can be coupled to the valve body. Each of the plurality of leaflets can have an open position and a closed position. Each of the plurality of leaflets can have a line that extends from the bottom point of the leaflet to the center of the free margin. One or more of the plurality of leaflets comprises two or more features. The features comprise an axis. The inclination of the axis of the features with respect to the line should be less than 10 degrees.
In general, in another aspect, the invention can include a heart valve comprising a valve body and a plurality of flexible leaflets coupled to the valve body. The plurality of leaflets should have an open position and a closed position. Each of the plurality of leaflets can comprise a belly when the plurality of leaflets are in their respective closed positions. The belly of one or more of the plurality of leaflets preferably has a continuous curvature except for a non-continuous portion. Alternatively, each leaflet can comprise a belly having a predominately first curvature in the open position and a predominately second curvature in the closed position.
In general, in another aspect, the invention can include a heart valve comprising a valve body and a plurality of flexible leaflets coupled to the valve body. Each leaflet has a thickness. One or more of the plurality of leaflets can comprise a buckle-susceptible portion, the thickness of the buckle-susceptible portion being different from the thickness of the remaining portion of the leaflet.
In general, in another aspect, the invention can include a heart valve comprising a valve body and a plurality of flexible leaflets coupled to the valve body. The plurality of leaflets should have an open position and a closed position. One or more of the plurality of leaflets can comprise an expansion feature such a folded, peaked or ridged region. The expansion feature is preferably configured so that the leaflet has more surface area in the open position than it has in the closed position.